The problem is they pull it in and leave the electric on. It drains the batteries down to the point the ICE kicks on hours later to maintain the battery charge, filling the garage with CO/CO2/etc.
but isn’t there an indicator light telling you that the engine or even battery is off? Or how about an indicator noise? If the Volt doesn’t have a noise, and my 2006 Saturn Ion has a noise telling you that the car isn’t entirely turned off?